DataSheet8_Fucoidan Alleviates Renal Fibrosis in Diabetic Kidney Disease via Inhibition of NLRP3 Inflammasome-Mediated Podocyte Pyroptosis.ZIP

Background: Fucoidan (FPS) has been widely used to treat renal fibrosis (RF) in patients with diabetic kidney disease (DKD); however, the precise therapeutic mechanisms remain unclear. Recently, research focusing on inflammation-derived podocyte pyroptosis in DKD has attracted increasing attention. This phenomenon is mediated by the activation of the nucleotide-binding oligomerization domain (Nod)-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, leading to RF during DKD progression. Therefore, we designed a series of experiments to investigate the ameliorative effects of FPS on RF in DKD and the mechanisms that are responsible for its effect on NLRP3 inflammasome-mediated podocyte pyroptosis in the diabetic kidney.
Methods: The modified DKD rat models were subjected to uninephrectomy, intraperitoneal injection of streptozotocin, and a high-fat diet. Following induction of renal injury, the animals received either FPS, rapamycin (RAP), or a vehicle for 4 weeks. For in vitro research, we exposed murine podocytes to high glucose and MCC950, an NLRP3 inflammasome inhibitor, with or without FPS or RAP. Changes in the parameters related to RF and inflammatory podocyte injury were analyzed in vivo. Changes in podocyte pyroptosis, NLRP3 inflammasome activation, and activation of the adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin complex 1 (mTORC1)/NLRP3 signaling axis involved in these changes were analyzed in vivo and in vitro.
Results: FPS and RAP ameliorated RF and inflammatory podocyte injury in the DKD model rats. Moreover, FPS and RAP attenuated podocyte pyroptosis, inhibited NLRP3 inflammasome activation, and regulated the AMPK/mTORC1/NLRP3 signaling axis in vivo and in vitro. Notably, our data showed that the regulative effects of FPS, both in vivo and in vitro, on the key signaling molecules, such as p-AMPK and p-raptor, in the AMPK/mTORC1/NLRP3 signaling axis were superior to those of RAP, but similar to those of metformin, an AMPK agonist, in vitro.
Conclusion: We confirmed that FPS, similar to RAP, can alleviate RF in DKD by inhibiting NLRP3 inflammasome-mediated podocyte pyroptosis via regulation of the AMPK/mTORC1/NLRP3 signaling axis in the diabetic kidney. Our findings provide an in-depth understanding of the pathogenesis of RF, which will aid in identifying precise targets that can be used for DKD treatment.

背景：褐藻多糖硫酸酯（Fucoidan, FPS）已被广泛用于治疗糖尿病肾病（Diabetic Kidney Disease, DKD）患者的肾纤维化（Renal Fibrosis, RF），但其确切的治疗机制仍不明确。近年来，聚焦于糖尿病肾病中炎症介导的足细胞焦亡的研究受到越来越多的关注。该现象由核苷酸结合寡聚化结构域样受体家族含pyrin结构域蛋白3（Nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3, NLRP3）炎性体的激活所介导，在糖尿病肾病进展过程中引发肾纤维化。因此，本研究设计了一系列实验，以探究FPS对糖尿病肾病肾纤维化的改善作用，及其在糖尿病肾脏中调控NLRP3炎性体介导的足细胞焦亡的潜在机制。
方法：本研究采用改良的糖尿病肾病大鼠模型，该模型通过单侧肾切除、腹腔注射链脲佐菌素（Streptozotocin）并配合高脂饲料构建。在肾损伤造模成功后，将大鼠随机分为褐藻多糖硫酸酯组、雷帕霉素（Rapamycin, RAP）组及溶剂对照组，连续给药4周。体外实验方面，将小鼠足细胞置于高糖环境中培养，并分别联合或不联合褐藻多糖硫酸酯、雷帕霉素，以及NLRP3炎性体抑制剂MCC950。在体内实验中，分析与肾纤维化及炎症性足细胞损伤相关的各项指标变化；在体内及体外实验中，均分析足细胞焦亡、NLRP3炎性体激活，以及腺苷酸活化蛋白激酶（Adenosine Monophosphate-activated Protein Kinase, AMPK）/雷帕霉素靶蛋白复合物1（Mammalian Target of Rapamycin Complex 1, mTORC1）/NLRP3信号轴的激活变化。
结果：褐藻多糖硫酸酯与雷帕霉素均可改善糖尿病肾病模型大鼠的肾纤维化及炎症性足细胞损伤。此外，二者在体内及体外实验中均能减轻足细胞焦亡、抑制NLRP3炎性体激活，并调控AMPK/mTORC1/NLRP3信号轴。值得注意的是，本研究数据显示，褐藻多糖硫酸酯在体内外对AMPK/mTORC1/NLRP3信号轴中的关键信号分子（如p-AMPK与p-raptor）的调控效果优于雷帕霉素，且在体外实验中与AMPK激动剂二甲双胍（Metformin）的调控效果相近。
结论：本研究证实，褐藻多糖硫酸酯与雷帕霉素类似，可通过调控糖尿病肾脏中的AMPK/mTORC1/NLRP3信号轴，抑制NLRP3炎性体介导的足细胞焦亡，从而缓解糖尿病肾病患者的肾纤维化。本研究结果加深了对肾纤维化发病机制的理解，可为糖尿病肾病的精准治疗靶点筛选提供理论依据。